1. Field of the Invention
The present invention pertains to a device and method for treating heart disease. More particularly, the present invention is directed to a method and device for treating congestive heart disease and related valvular dysfunction.
2. Description of the Prior Art
Congestive heart disease is a progressive and debilitating illness. The disease is characterized by a progressive enlargement of the heart. As the heart enlarges, the heart is performing an increasing amount of work in order to pump blood each heart beat. In time, the heart becomes so enlarged the heart cannot adequately supply blood. An afflicted patient is fatigued, unable to perform even simple exerting tasks and experiences pain and discomfort. Further, as the heart enlarges, the internal heart valves cannot adequately close. This impairs the function of the valves and further reduces the heart""s ability to supply blood.
Causes of congestive heart disease are not fully known. In certain instances, congestive heart disease may result from viral infections. In such cases, the heart may enlarge to such an extent that the adverse consequences of heart enlargement continue after the viral infection has passed and the disease continues its progressively debilitating course.
Commonly assigned U.S. Pat. No. 5,702,343 to Alferness dated Dec. 30, 1997 discloses a jacket of biologically compatible material adapted to surround the heart and to be secured to the heart. The jacket is adjustable such that it may be adjusted to snugly conform to an external geometry of the heart and constrain circumferential expansion of the heart beyond the maximum adjusted volume during diastole while permitting unimpeded contraction of the heart during systole. The present invention pertains to an adjustment clamp for adjusting a cardiac support device such as that disclosed in the ""343 patent.
The present invention provides an adjustment clamp suitable for adjusting the tension of a material such as a cardiac support device. The adjustment clamp comprises a pair of intersecting arms interconnected about a common axis wherein the arms are capable of rotating around the common axis. The arms each comprise a handle, a jaw and a shaft connecting the handle and jaw. The handle preferably comprises a finger loop and a latch attached on the inferior surface of the handle. When the handles are pulled together, the latching surface of each latch causes the two arms to interconnect with each other, thereby locking the clamp at a desired position. The jaws of each arm comprise a clamping surface that is operably engaged when the handles are rotated toward each other. In one embodiment, the jaw comprises at least one roller assembly that comprises at least one roller. According to this embodiment, the clamping surface includes the tangent of the roller. The roller assembly may be rotatably mounted within a frame. Preferably, the clamp also includes a turning mechanism operably mounted to at least one roller assembly.
In use, the handles of the clamp are rotated apart and material (for example, a jacket of a cardiac support device) is positioned in contact with the clamping surface. The handles of the clamp are rotated towards one another such that clamping surface engages the material.
According to the invention, the clamping surfaces are biased together such that the clamping force is less than the desired tension of the fabric. When used in connection with a cardiac support device, it is important that the fabric tension not impair cardiac function. Therefore, the clamping force is preferably less than the left ventricular pressure during diastole.
Once the clamp is biased at a desired clamping force, the material is pulled through the clamp. In the roller clamp embodiment, a turning mechanism is rotated to cause at least one roller to rotate. The frictional contact and clamping force between the rollers urges the material between the rollers, thus increasing tension of the material.
The clamping force of the clamping surface may optionally be varied by the position at which the latch is engaged. The clamp is capable of securing the material until the material reaches a tension wherein the load exerted by the material exceeds the clamping force exerted between the clamping surface (also called the xe2x80x9ctension limitxe2x80x9d). In the roller clamp embodiment, the rollers may continue to rotate after the tension limit is reached, but material is no longer urged between the rollers. Advantageously, the rollers will slip in areas where the tension of the material has reached the tension limit but will continue to urge material between the rollers in other areas where the tension limit has not yet been reached, until the tension across the material is substantially uniform (e.g., at the tension limit).